To my mind, you can't really compare the Palms and Blue Tang, straight across. There are some things I really like about Blue Tang and there are others that I prefer about the Palms. The Palms is a cut, or maybe two above, with a very good location and beach area. It has private balconies and the Blue Tang has common verandas. Sometimes, the music and partying from Wet Willies, at the end of the dock out front, can get a bit annoying.
The front suites in the Blue Tang, on the second and especially on the third floor are marvelous. The pool is very small, more for wading than anything, but the deck is cute. If you end up in a unit on the north side of the building, it is right next to a side street, that can get pretty noisy, especially in the am. The beach out front is not that great, whereas the beach at the Palms . . .it is right next door to Ramon's and that is a fairly nice stretch of beach for San Pedro.
Sorry, I am not familiar with Caye Casa. However, if it is in the area you mentioned, I do generally favor the Boca del Rio area. Before you book it though, you should probably be aware that the beach in front has a vehicular road, and not just foot traffic. It's not that busy, just something I think you'd want to be aware of before you got there.